1. Field of the Invention
The present invention relates to exercise devices and more particularly to an exercise device for weight training for the purpose of developing lower body muscles and tendons and general body conditioning.
2. Description of the Prior Art
It is common in athletes to work out with weights as a means of developing the levels of strength needed in competitions. In lifting rigid weights, however, due to gravity, the velocity is generally inversely proportional with the load, that is the higher the load the lower the velocity and vice-versa. For this reason the value of lifting rigid weights as a means of muscle conditioning is less useful for certain athletic activities for which a fast, explosive type muscular power is required. On the other hand, simulating in training both the high load and the high velocity typical for competitions is desired. In this respect, for propulsion-type athletic activities like jumping and sprint running it would be advantageous if a direct relationship between the load and the velocity could be achieved so that higher speed levels characteristic for competitions could be attained when training with weights.
Based on various criteria, the literature describes different types of muscular contractions associated with the development of strength: isotonic, isometric, isokinetic, with variable resistance, plyometric etc. Insufficiently differentiated are the muscular contractions associated with decelerating and accelerating body movements, although their succession is common in running and jumping as well as in other activities.
For the purpose of this invention, the muscular activity associated with an acceleration movement is described as an "expometric" contraction, and that associated with a deceleration movement is described as an "expotonic" contraction.
For the purpose of the specification and claims the term "expotonic" refers to the muscular contractions that occur in decelerated movements and the initiation of new movements (cycles) such as flexing a member before an impulsion. An example could be the support phase in sprint running when the body inertia acts as a compounding factor in tensioning the flexing leg's muscles and tendons. In "expotonic" type muscular contractions the kinetic energy is transformed in potential energy and stored in the participating muscles and tendons.
The term "expometric" refers to muscular contractions associated with the fast release of a flexed member when a portion of the potential energy is transformed back into kinetic energy. This type of muscular activity is present in the impulsion phase of sprint running, characterized by the accelerated extension of the supporting leg. The impulsion is enhanced by the powerful eccentric work by arms and the oscillating leg, which further accelerate the motion of the entire body, facilitating the take-off.